Nighttime Exposure To Blue Light Could Encourage Sugary Snack Consumption (In Rats)

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In our screen-addled age, blue light is an unavoidable part of daily life. It radiates from your work desktop, your smartphone, and even the energy-saving LED lights you installed in the kitchen.

While research into the negative health effects of blue light is not fully conclusive, it has been linked to various ailments from cancer and diabetes to heart disease, obesity, and poorer sleep. To add to that list, scientists presenting at this year’s conference of the Society for the Study of Ingestive Behavior (SSIB) say that blue light can trigger excessive sugary snack consumption – at least in rats.

The study found an hour of blue light exposure at night (aka: just enough time to watch an episode of The Crown or precisely six-tenths of Finding Nemo) led to elevated blood sugar levels and increased sugar consumption among male rats. The researchers note that their glucose-tolerance levels changed post-exposure – a warning sign of pre-diabetes.

Over the course of the study, the rats had their choice of nutritionally balanced food (i.e. standard rodent food), water, lard, and sugar water. When exposed to blue light at night – even for as short a time as one hour – they drank more sugar than when not. The rats were tested following a night of blue light exposure but more consistent exposure levels could result in weight gain and a diabetes diagnosis.

Though it is important to note that these observations were made in rats (and male rats specifically), the researchers warn that a similar process could be at work in people (and men, in particular) who are tied to their screens.

“Limiting the amount of time that we spend in front of screens at night is, for now, the best measure to protect ourselves from the harmful effects of blue light,” said Anayanci Masís-Vargas from the University of Strasbourg, France, in a statement. “In case it is necessary to be exposed to devices at night, I would recommend the use of apps and night mode features on the devices, which turn the screens more orange and less blue or the use of blue light filtering googles that are already available in the market.”

While the study has thrown up some interesting results, future studies will hopefully confirm whether or not the findings can be replicated in humans. As we have found time and time again (often to our detriment), animal models are a useful but not necessarily fool-proof method of biomedical research and what may be true in rats (or mice) may not be true in humans.

What’s more, many studies (including the one here) limit the trials to one sex, usually male. In practice, this may mean the results apply less to women than they do to men.  

It might also be worth remembering that while blue light has received a lot of negative press lately, it’s not all bad. Indeed, the vast majority of blue light exposure comes from the sun and during daytime can boost attention, reaction times, and mood. The problem comes at night when it can push the circadian rhythm out of whack, making it harder to sleep.

Rahul Khurana, MD, a spokesperson for the American Academy of Ophthalmology, recommends limiting screen time two to three hours before bed – or switching to a nighttime setting if necessary.

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